Protective helmet



FIG. 1 is a left side view of a protective helmet showing my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a front-left perspective view thereof; and,

FIG. 7 is a front-right perspective view thereof.

The broken line showing of portions of the protective helmet depicts environment and forms no part of the claim. 

CLAIM I claim the ornamental design for a protective helmet, as shown and described. 